Cleaning device for gas passages in percussion machines



Aug. 14, 1962 G. A. BERGMAN CLEANING DEVICE FOR GAS PASSAGES IN PERCUSSION MACHINES Filed March 9, 1961 United States Patent Ofiice 3,649,1(93 Patented Aug. 14, 1962 3,tl49,108 CLEANTNG liEVl'iCE FUR GAS PASdAGES IN PERCUSEN MACEHNES Gustav Albert Bergman, Baldersvagen 20, Danderyd, Sweden Filed Mar. 9, 1961, Ser. No. 94,5tl Claims priority, application Sweden Mar. 21, E60 4 Claims. (Cl. 123-7) The present invention relates to such percussion machines, for example rock drills or breaking machines, which are provided with a freely running hammer piston with an auxiliary piston in the hammer piston cylinder and in which the running hammer piston is connected with the cylinder of a combustion engine. In machines of this kind the auxiliary piston limits on one side a gas chamber, which communicates with the combustion chamber by a passage, usually in the form of a bore in the cylinder wall. This passage, through which the combustion gas is forced down to the gas chamber to form a gas cushion for the return movement of the hammer piston, has a tendency after a fairly short period of operation to be covered with soot and other combustion remains, and consequently it often requires to be cleaned. This frequently recurring cleaning requires apart from the actual cleaning, work time for dismantling, which is necessary if the passage is to be accessible for cleaning tools.

The object of the invention is to reduce or completely eliminate the manual work of cleaning of gas conducting passages in this kind of machine, so that as far as possible the cleaning is automatic. For this purpose, according to the invention, the gas conducting passage is provided with a loose insert, preferably a metal wire, which as a result of the shaking of the machine during operation, is kept in movement in the passage and thereby prevents the deposition of combustion remains and the like on the walls of the passage. The insert may advantageously be made of such material that it, under the action of the hot combustion gases becomes red hot, and in this way assists in achieving a certain degree of after combustion of uncombusted material which may enter the passage. A simple and reliable insert can in practice be obtained by piano wire, which is provided with an abutment so that it is held in a suitable place in the passage. This abutment can be obtained by bending back the end of the wire, so that the wire can be arranged with the bent end in an extension at the lower end of the passage.

The invention is illustrated in the drawings by means of an embodiment. FIGURE 1 shows a part of a combustion driven rock drill machine, partly in axial section. FIGURE 2 shows on a larger scale an axial section through the lower part of the passage with the cleaning member arranged in it. FIGURE 3 is an elevation of a modified insert.

In the drawings, designates a freely running hammer piston, which has the shape of a differential piston having a small diameter piston part 1 in the motor cylinder 12 and an auxiliary piston 16 having a larger diameter. The auxiliary piston is movable in a hammer piston cylinder 13 which forms a downward continuation of the motor cylinder 12. The combustion chamber of the motor is limited at the bottom by the piston part 14 of the hammer piston and at the top by the motor piston 22. The hammer piston has at its lower end a piston rod 24, whose lower end in a manner known for this kind of machine strikes the upper end of a drill tool 25.

The cylinder space 2t) of the hammer piston cylinder on the opposite of the auxiliary piston 16 to the motor cylinder communicates through a passage 44 having a one-way valve 46 with the cylinder space 20, in which a gas cushion for returning the hammer piston is formed. The passage 44 opens through a part 48 into the cylinder space 42 some distance from the latters lower end wall 28. Every explosion in the combustion chamber 20 forces combustion gases down through the passage and the one-Way valve 46 into the cylinder space 42 in order to return the hammer piston after its downward work stroke.

There is an insert in the form of a metal Wire 50, preferably a steel wire, in the passage 44; the wire is narrower than the passage and sits loosely in it, so that the wire during the shaking which occurs when the machine is operating can move not only upwardly and downwardly but also sidewardly. So that the upper end of the wire which is situated somewhat adjacent the opening of the passage in the wall of the motor cylinder 20 shall not enter the cylinder space, the wire may be provided with a stop, which limits movement in the longitudinal direction of the passage. This is, as shown in FIGURE 2, achieved by bending the lower end of the wire upwardly so that it engages a step 52 formed in a counterbore between a lower extended part 54 of the passage and the rest of the passage. Downward movement of wire is limited by the valve housing of the valve 4-5, which after the wire has been placed in the passage is screwed into position in a threaded bore in the cylinder wall. When the machine is in operation, the wire becomes red hot owing to the heat from the combustion gases and in this way it assists in effecting the final combustion of a part of the gases accompanying the unburned particles. Soot deposit in the passage is therefore prevented by the wires continual movements in the passage and its rubbing against the walls of the passage owing to the shaking of the machine during drilling work.

Cleaning members similar to those just described can be placed in air passages in such machines in which the hammer pistons movement in the one or other direction is achieved by means of compressed air.

The modified insert shown in FIG. 3 consists of a straight wire or rod 56 and sleeve or nut 58 secured at the lower end of the rod which also has its end surface covered by a rounded head 60 of a material of great strength such as Stellite (the trademark of Haynes Stellite Co., for certain cobalt-chromium alloys). The rod is adapted to have its sleeve 58 located in the widened counterbore 54 to form a stop by the top surface 62 of the sleeve.

What I claim is:

1. In a combustion engine driven percussion machine a cleaning device for a downwardly directed passage passed by combustion gases, comprising a rod having one end enlarged and strengthened and being loosely arranged in the passage, said rod being adapted to be maintained in movement in said passage during the operation of the engine as a result of the shaking of the machine during its operation.

2. In a combustion engine driven percussion machine a cleaning device for a passage passed by combustion gases, comprising an insert in the form of a wire loosely arranged in the passage and extending longitudinally thereof, said wire being adapted to be maintained in movement in said passage during the operation of the engine solely as a result of the shaking of the machine during its operation.

3. A combustion engine driven percussion machine comprising a combustion engine cylinder, an engine piston in said cylinder, a hammer piston cylinder, a hammer piston combined with an auxiliary piston adapted to run freely in said hammer piston cylinder, a passage bore for gases being provided in the cylinder wall. of the engine cylinder and of the hammer piston cylinder, said passage bore having a widened part, a cleaning device for said passage comprising a wire extending longitudinally of said passage bore and provided with a double bent portion in said widened part, the wire being loosely mounted in the passage bore to be able to oscillate therein as a result of the shaking of the machine during its operation.

4. In percussion machines having hammer pistons operated by compressed air, a cleaning device for an air passage comprising a rod loosely mounted in the passage to clean the passage due to movements caused by the shaking of the machine.

References Cited in the file of this patent UNITED STATES PATENTS 2,214,800 Smith Sept. 17, 1940 2,551,988 Weyandt May 8, 1951 2,684,055 Bergman July 20, 1954 FOREIGN PATENTS 488,549 Great Britain July 11, 1938 OTHER REFERENCES Bergman, German Application, 1,036,188 printed August 14, 1958 (Kl.5b10). 

